protection against infection
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Pathogens ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 93
Author(s):  
Laura Del Rio ◽  
Antonio Murcia-Belmonte ◽  
Antonio Julián Buendía ◽  
Jose Antonio Navarro ◽  
Nieves Ortega ◽  
...  

Mice are valuable models extensively used to test vaccine candidates against Chlamydia abortus and to clarify immunopathological mechanisms of the bacteria. As this pathogen has the ability to reactivate during pregnancy, it is important to deepen the knowledge and understanding of some of the effects of female hormones on immunity and vaccination. This study is aimed at describing the role of sex hormones in the pathology of OEA during chlamydial clearance using ovariectomised mice and also gaining an understanding of how 17β-oestradiol or progesterone may impact the effectiveness of vaccination. Animals were treated with sex hormones and infected with C. abortus, and the kinetics of infection and immune response were analysed by means of bacterial isolation, histopathology, and immunohistochemistry. In a second phase of the study, protection conferred by an experimental vaccine after hormone treatment was assessed. Oestradiol showed a stimulatory effect on the immune response during infection, with a more efficient recruitment of macrophages and T-cells at the infection site. Furthermore, after vaccination, oestradiol-treated animals showed a stronger protection against infection, indicating that this hormone has a positive effect, stimulating a specific memory response to the pathogen.


2022 ◽  
Author(s):  
Anneliese Ashhurst ◽  
Matt Johansen ◽  
Joshua Maxwell ◽  
Caroline Ashley ◽  
Anupriya Aggarwal ◽  
...  

Abstract Current vaccines against SARS-CoV-2 substantially reduce mortality, but protection against infection is less effective. Enhancing immunity in the respiratory tract, via mucosal vaccination, may provide protection against infection and minimise viral spread. We tested a novel subunit vaccine in mice, consisting of SARS-CoV-2 Spike protein with a TLR2-stimulating adjuvant, delivered to mice parenterally or mucosally. Both routes of vaccination induced substantial neutralising antibody (nAb) titres, however, mucosal vaccination uniquely generated anti-Spike IgA, increased nAb in the serum and airways, and increased lung CD4+ T-cell responses. TLR2 is expressed by respiratory epithelia and immune cells. Using TLR2 deficient chimeric mice, we determined that TLR2 expression in either compartment facilitated early innate responses to mucosal vaccination. By contrast, TLR2 on hematopoietic cells was essential for optimal lung-localised, antigen-specific responses. In a K18-hACE2 mice, vaccination provided complete protection against disease and sterilising lung immunity against SARS-CoV-2. These data support mucosal vaccination as a strategy to improve protection in the respiratory tract against SARS-CoV-2 and other respiratory viruses.


2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Ian F. Miller ◽  
C. Jessica E. Metcalf

The evolution of SARS-CoV-2 virulence, or lethality, threatens to exacerbate the burden of COVID-19 on society. How might COVID-19 vaccines alter selection for increased SARS-CoV-2 virulence? Framing current evidence surrounding SARS-CoV-2 biology and COVID-19 vaccines in the context of evolutionary theory indicates that prospects for virulence evolution remain uncertain. However, differential effects of vaccinal immunity on transmission and disease severity between respiratory compartments could select for increased virulence. To bound expectations for this outcome, we analyse an evo-epidemiological model. Synthesizing model predictions with vaccine efficacy data, we conclude that while vaccine-driven virulence remains a theoretical possibility, the risk is low if vaccines provide sustained robust protection against infection. Furthermore, we found that any increases in transmission concomitant with increases in virulence would be unlikely to threaten prospects for herd immunity in a highly immunized population. Given that virulence evolution would nevertheless impact unvaccinated individuals and populations with low vaccination rates, it is important to achieve high vaccination rates worldwide and ensure that vaccinal immunity provides robust protection against both infection and disease, potentially through the use of booster doses.


2021 ◽  
Author(s):  
Fayette Klaassen ◽  
Melanie H Chitwood ◽  
Ted Cohen ◽  
Virginia E Pitzer ◽  
Marcus Russi ◽  
...  

Importance: Prior infection and vaccination both contribute to population-level SARS-CoV-2 immunity. Population-level immunity will influence future transmission and disease burden. Objective: For each US county and state, we estimated the fraction of the population with prior immunological exposure to SARS-CoV-2 (ever infected with SARS-CoV-2 and/or received one or more doses of a COVID-19 vaccine) as well as the fraction with effective protection against infection and severe disease from prevalent SARS-CoV-2 variants, from January 1st, 2020, to October 31st, 2021. Design, settings, participants: We used daily SARS-CoV-2 infection estimates for each US state and county, derived based on reported data on COVID-19 cases and deaths. We collated county-level vaccination coverage data and estimated the fraction of individuals both vaccinated and previously infected using the Census Bureau Household Pulse Survey. We used published evidence on natural and vaccine-induced immunity, and how protection wanes over time. We used a Bayesian model to synthesize evidence and estimate population immunity outcomes. Main Outcomes and Measures: Primary outcomes were the fraction of the population with (i) a history of exposure to SARS-CoV-2 infection or COVID-19 vaccination or both, (ii) effective protection against infection, and (iii) effective protection against severe disease. We estimated outcomes for each US state and county from January 1st, 2020, to October 31st, 2021. Results: The estimated percentage of the US population with a history of SARS-CoV-2 infection or vaccination, as of October 31, 2021, was 86.2% (95%CrI: 82.2%-93.0%), compared to 24.9% (95%CrI: 18.5%-34.1%) on January 1, 2021. State-level estimates for October 31, 2021, ranged between 72.2% (95%CrI: 62.5%-83.3%, West Virginia) and 92.3% (95%CrI: 88.6%-96.1%, Florida). Accounting for waning, the effective protection against infection with prevalent strains as of October 31 was 49.9% (95%CrI: 45.4%-56.6%) nationally and ranged between 37.2% (95%CrI: 33.4%-44.7%, Vermont) and 59.5% (95%CrI: 56.4%-66.0%, Florida). Effective protection against severe disease was 77.4% (95%CrI: 73.7%-83.4%) nationally and ranged between 62.9% (95%CrI: 55.2%-73.3%, West Virginia) and 83.8% (95%CrI: 80.7%-88.0%, Florida). Conclusions and Relevance: The fraction of the population with effective protection against SARS-CoV-2 infection and severe COVID-19 varies across the United States, but a substantial proportion of the population remains susceptible.


2021 ◽  
Author(s):  
Christian Holm Hansen ◽  
Astrid Blicher Schelde ◽  
Ida Rask Moustsen-Helms ◽  
Hanne-Dorthe Emborg ◽  
Tyra Grove Krause ◽  
...  

In this brief communication we are showing original research results with early estimates from Danish nationwide databases of vaccine effectiveness (VE) against the novel SARS-CoV-2 Omicron variant (B.1.1.529) up to five months after a primary vaccination series with the BNT162b2 or mRNA-1273 -19 vaccines. Our study provides evidence of protection against infection with the Omicron variant after completion of a primary vaccination series with the BNT162b2 or mRNA-1273 vaccines; in particular, we found a VE against the Omicron variant of 55.2% (95% confidence interval (CI): 23.5 to 73.7%) and 36.7% (95% CI: 69.9 to 76.4%) for the BNT162b2 and mRNA-1273 vaccines, respectively, in the first month after primary vaccination. However, the VE is significantly lower than that against Delta infection and declines rapidly over just a few months. The VE is re-established upon revaccination with the BNT162b2 vaccine (54.6%, 95% CI: 30.4 to 70.4%).


2021 ◽  
Vol 12 ◽  
Author(s):  
Xiao-Jie Xu ◽  
Qing Zhu ◽  
Shao-Yan Jiang ◽  
Zhi-Yong Yan ◽  
Chao Geng ◽  
...  

Sugarcane mosaic virus (SCMV; genus Potyvirus) induces maize dwarf mosaic disease that has caused serious yield losses of maize in China. Cross-protection is one of the efficient strategies to fight against severe virus strains. Although many mild strains have been identified, the spontaneous mutation is one of the challenging problems affecting their application in cross-protection. In this study, we found that the substitution of cysteine (C) at positions 57 or 60 in the zinc finger-like motif of HC-Pro with alanine (A; C57A or C60A) significantly reduced its RNA silencing suppression activity and SCMV virulence. To reduce the risk of mild strains mutating to virulent ones by reverse or complementary mutations, we obtained attenuated SCMV mutants with double-mutations in the zinc finger-like and FRNK motifs of HC-Pro and evaluated their potential application in cross-protection. The results showed that the maize plants infected with FKNK/C60A double-mutant showed symptomless until 95 days post-inoculation and FKNK/C60A cross-protected plants displayed high resistance to severe SCMV strain. This study provides theoretical and material bases for the control of SCMV through cross-protection.


2021 ◽  
Author(s):  
Laith J Abu-Raddad ◽  
Hiam Chemaitelly ◽  
Houssein H. Ayoub ◽  
HADI M. YASSINE ◽  
Fatiha Benslimane ◽  
...  

BACKGROUND: In early 2021, Qatar launched a mass immunization campaign with Moderna mRNA-1273 COVID-19 vaccine. We assessed persistence of real-world mRNA-1273 effectiveness against SARS-CoV-2 infection and against COVID-19 hospitalization and death. METHODS: Effectiveness was estimated using test-negative, case-control study design, between January 1 and December 5, 2021. Effectiveness was estimated against documented infection (a PCR-positive swab, regardless symptoms), and against any severe (acute-care hospitalization), critical (ICU hospitalization), or fatal COVID-19. RESULTS: By December 5, 2021, 2,962 breakthrough infections had been recorded among those who received two mRNA-1273 doses. Of these infections, 19 progressed to severe COVID-19 and 4 to critical, but none to fatal disease. mRNA-1273 effectiveness against infection was negligible for the first two weeks after the first dose, increased to 65.5% (95% CI: 62.7-68.0%) 14 or more days after the first dose, and reached its peak at about 90% in the first three months after the second dose. Effectiveness declined gradually starting from the fourth month after the second dose and was below 50% by the 7th month after the second dose. Effectiveness against severe, critical, or fatal COVID-19 reached its peak at essentially 100% right after the second dose, and there was no evidence for declining effectiveness over time. Effectiveness against symptomatic versus asymptomatic infection demonstrated the same pattern of waning, but effectiveness against symptomatic infection was consistently higher than that against asymptomatic infection and waned more slowly. CONCLUSIONS: mRNA-1273-induced protection against infection appears to wane month by month after the second dose. Meanwhile, protection against hospitalization and death appears robust with no evidence for waning for several months after the second dose.


2021 ◽  
Author(s):  
Chadi M Saad-Roy ◽  
Simon A Levin ◽  
Julia Rose Gog ◽  
Jeremy Farrar ◽  
Caroline E Wagner ◽  
...  

Vaccination provides a powerful tool for mitigating and controlling the COVID-19 pandemic. However, a number of factors reduce these potential benefits. The first problem arises from heterogeneities in vaccine supply and uptake: from global inequities in vaccine distribution, to local variations in uptake derived from vaccine hesitancy. The second complexity is biological: though several COVID-19 vaccines offer substantial protection against infection and disease, 'breakthrough' reinfection of vaccinees (and subsequent retransmission from these individuals) can occur, driven especially by new viral variants. Here, using a simple epidemiological model, we show that the combination of infection of remaining susceptible individuals and breakthrough infections of vaccinees can have significant effects in promoting infection of invading variants, even when vaccination rates are high and onward transmission from vaccinees relatively weak. Elaborations of the model show how heterogeneities in immunity and mixing between vaccinated and unvaccinated sub-populations modulate these effects, underlining the importance of quantifying these variables. Overall, our results indicate that high vaccination coverage still leaves no room for complacency if variants are circulating that can elude immunity, even if this happens at very low rates.


2021 ◽  
Author(s):  
Billy J Gardner ◽  
A. Marm Kilpatrick

The emergence of the Omicron variant (B.1.1.529) of SARS-CoV-2 has raised concerns about how mutations in the spike protein might influence immune escape and vaccine protection against infection and disease, COVID-19. Initial estimates of immune escape measure neutralizing antibody titers, which have been shown to be a correlate of protection for COVID-19, but vary among studies. However, no studies have examined variation in vaccine effectiveness (VE) using estimated reductions in neutralizing antibody titers across virus variants. We quantified consistency in relative neutralizing antibody titers across studies. We then examined relationships between variant-specific reductions in neutralizing antibodies and protection against documented infection, symptomatic disease, and hospitalizations across variants and vaccines. We found considerable variation in variant-specific neutralizing antibody titers between studies, but within-study comparisons across variants were far more robust. There was insufficient data to estimate VE for a single vaccine across variants, especially for higher levels of immune evasion (>7-fold reductions in neutralizing antibody titers) observed with the Omicron variant (40-fold). Instead, we leveraged variation among both vaccines and virus variants to estimate VE - neutralizing antibody titer relationships across a 30 to 100-fold range of neutralizing antibody titers reduction. Omicron increased the risk of hospitalization four to five-fold and increased the risk of symptomatic disease seven to ten-fold for mRNA vaccinees, with similar relative effects for recently vaccinated, or individuals with waned antibody titers. Third doses restored titers and protection to levels similar to waned immunity against Delta. Overall, these analyses indicate that vaccine effectiveness against severe disease is significantly diminished for waned individuals, and protection against infection, symptomatic disease and transmission is nearly eliminated. However, third doses significantly ameliorate these reductions but only restore protection to levels equivalent to waned protection against the Delta variant. The invasion of Omicron is likely to result in widespread infection, and substantial hospitalizations unless widespread boosting of immunity occurs.


Vaccines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1457
Author(s):  
Priscila Diniz Lopes ◽  
Cintia Hiromi Okino ◽  
Filipe Santos Fernando ◽  
Caren Pavani ◽  
Viviane Casagrande Mariguela ◽  
...  

Efficient vaccines are the main strategy to control the avian coronavirus (AvCoV), although several drawbacks related to traditional attenuated and inactivated vaccines have been reported. These counterpoints highlight the importance of developing new alternative vaccines against AvCoV, especially those able to induce long-lasting immune responses. This study evaluated and compared two inactivated vaccines formulated with AvCoV BR-I variants, one composed of chitosan nanoparticles (AvCoV-CS) and the second by Montanide oily adjuvant (AvCoV-O). Both developed vaccines were administered in a single dose or associated with the traditional Mass attenuated vaccine. The AvCoV-CS vaccine administered alone or associated with the Mass vaccine was able to induce strong humoral and cell-mediated immune (CMI) responses and complete protection against IBV virulent infection, wherein single administration was characterized by high IgA antibody levels in the mucosa, whereas when associated with the Mass vaccine, the serum IgG antibody was predominantly observed. On the other hand, single administration of the oily vaccine presented poor humoral and CMI responses and consequently incomplete protection against virulent challenge, but when associated with the Mass vaccine, immune responses were developed, and complete protection against infection was observed. Both of our experimental vaccines were able to induce full protection against virulent IBV challenge. A single dose of AvCoV-CS vaccine was sufficient to achieve complete protection, while AvCoV-O required a previous priming by a Mass strain to complete the protection.


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